1. Field of the Invention
This invention relates to a device for tensioning flexible printing plates on a plate cylinder of a rotary printing machine by means of tensioning rails which are provided in a cylinder channel for clamping the two plate ends. The device includes means for securing the printing plate in register and under tension in a circumferential direction of the plate cylinder
2. Description of the Prior Art
Tensioning rails, which have been used in particular with sheet-fed printing machines, are usually mounted in slide guides provided in the cylinder channel. By adjusting means, such as adjusting screws, these tensioning rails, which clamp the ends of the printing plate, can be moved in a circumferential direction of the cylinder so that the printing plate itself can be secured under tension on the outer cylindrical surface of the plate cylinder. Furthermore, it is possible to stretch the trailing plate end or to move it in the axial direction in order to make up register differences. Such slide guides must feature narrow tolerances in order to be able to guarantee an adjustment of the tensioning rails free of play. Moreover, springs are needed for moving the tensioning rails back into their original position and for ensuring a play-free adjustment of the tensioning rails by the adjusting means. With offset printing presses, these slide guides are soiled very easily by the dampening solution and the solutions used for treating the plates, such as washing solutions. Consequently, the parts involved are subject to corrosion so that very precise mounting and tensioning of the printing plates could not be guaranteed.